Battery-powered portable devices are utilized for a wide variety of personal, commercial, and military applications. Examples of these devices include digital cameras, pocket-sized calculators and personal computers, personal digital assistant (PDA) devices, wireless telephones, laptop computers, camcorders, global positioning system (GPS) devices, portable entertainment systems, games, hand tools, and military and commercial communication devices. In other applications, batteries may be used for auxiliary purposes in larger devices, for example, in a motor vehicle or boat for starting the engine and providing low-level auxiliary power for small devices such as radios and cell phones.
The batteries used in most of these devices are rechargeable and are commonly defined as secondary batteries. Examples of secondary batteries include lithium ion, lithium polymer, nickel-cadmium, nickel-hydrogen, nickel-metal hydride, and lead acid batteries. Certain types of alkaline and zinc-air cells also may be used for secondary batteries.
Some of these devices have built-in charging systems, and others require separate charging systems for the secondary batteries. The design and operating characteristics of the charging systems usually are designed for each application, typically by the vendors of the devices which use the secondary batteries. Charging systems for batteries used in one type of device often are not interchangeable with those used in another type of device, and charging devices used for a given type of device may vary among the vendors of that type of device. The user of numerous devices operating on secondary batteries may require several different types of battery chargers, of which none may be interchangeable, and thus the user may have to carry several different types of battery chargers when using the devices in portable mode.
Secondary batteries typically are recharged by connection to an external power source such as a wall receptacle in a home or office or a power outlet in a motor vehicle. There are situations, however, when an external power source is not immediately available to recharge the secondary batteries in a device. In such cases, the user may have to carry disposable primary batteries, arrange access to a portable gasoline-powered generator, or arrange access to a charging system that operates on a large storage battery system. In most situations, however, these alternatives may be undesirable or unavailable.
There is a need in the art for a portable system to recharge secondary batteries when an external power source is not available. In addition, there is a need for a system that can recharge secondary batteries used in a wide variety of devices which under normal conditions would require different recharging systems. These needs are addressed by embodiments of the invention described below and defined by the claims that follow.